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CONSTRUCTION OF THE CB-1 VOICE RECORDER
The first thing we will do is locate the two PC boards used with this kit, and
then find where we will be starting construction. The smaller board, with the
3/8" hole in it, is called the display board. We'll construct it last since it has
finer traces, and a little practice on the bigger board will be of help. The
larger logic board is where we'll be starting.
If the two boards have not been separated already, you will want to separate
them before you start. To do this, simply place the board on the surface of a
table. Line up the area between the two boards over the edge of the table.
Pushing down evenly and carefully break the two boards apart. It is very
important to do this carefully. Breaking the board in the wrong spot will let
the chatter out of your chatterbox before you even begin to build it! Next,
take a file or emery board and smooth out any leftover material. When you
connect the two boards together later, a smooth edge is very important.
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1. Install power jack J4, soldering all three pins.
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2. Install voltage regulator VR1, 7805. Observe correct placement of the
metal tab. Mount it so the lettering on the case is facing the edge of the
board. The 7805 provides a stable source of 5 volts for the various IC
chips.
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3. Install C16, 10uF electrolytic capacitor. Electrolytic capacitors are
polarized and must be installed correctly. They are usually marked with a
black stripe and a ( - ) indicating their negative lead, while PC boards will
usually indicate the ( + ) hole.
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4. Install C18, .1uF disc capacitor (marked .1 or 104). This part helps
shape the resetting pulses for U4. This capacitor is a disc ceramic type
which has no polarity markings, so you may install it either way.
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5. Install Q7, 2N3904 NPN transistor. Notice the shape of the transistor.
The flat side must face the back of the board. This part helps to shape
the resetting pulses to U4.
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6. Install R18, 4.7K ohm resistor (yellow-violet-red).
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7. Install R19, 4.7K ohm resistor (yellow-violet-red).
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8. Install C15, 220uF electrolytic capacitor. Observe correct polarity. This
part helps smooth out the 12VDC input to the regulator, and to the audio
amplifier chip U2.
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9. Install C11, .1uF ceramic disc capacitor (marked .1 or 104). This part
helps reduce internal noise in the ISD1020 chip.
CB-1 • 8
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